The purpose of this project is to determine the causes of diabetic retinopathy and ultimately the optimal methods to prevent it. All participants in the Pima Indian Longitudinal Study of Diabetes are invited to have their retinas digitally photographed. The retinal photographs of participants with diabetes are read by local optometrists and those of participants without diabetes are read by NIDDK staff physicians to ensure that clinical issues are discovered and participants referred for appropriate treatment. Local optometrists have provided training for NIDDK staff physicians to conduct these low-risk readings. Batches of photographs are periodically sent for systematic reading for research purposes. The results of these systematic readings become the outcomes for analyses of predictors of diabetic retinopathy.